1. Field of the Invention
The present invention relates to an apparatus for laterally expanding a traveling web having longitudinal slits, which can be used in making non-woven fabric.
2. Background Art
A conventional method for producing non-woven fabric laminations comprises the steps of: preparing longitudinally elongated, split films 51 each having a lot of long or short slits longitudinally made therein; laterally expanding the split webs 51; and laying them crosswise on each other as shown in FIG. 9(a) to provide a non-woven fabric lamination. Otherwise, as shown in FIG. 9(b), longitudinally split-and-laterally expanded films 51 and laterally split-and-laterally expanded films 52 are alternately laid on each other to provide a non-woven fabric lamination. Non-woven fabric laminations thus provided are strong, light, stable in size, and air-permeable, and can be used as reinforcement materials.
A conventional net-like web expander comprises a curved application rod, a rubber roll, a screw roll having spiral grooves made on its circumference or a cloth guider which grip the opposite longitudinal edges of the net-like web to pull it wide.
Another conventional expander is called “Cage Roll”, which is shown for example, in Japan Patent Application, Publication No. S-46-43,275. It comprises a pair of disks facing each other, somewhat inclined toward each other, and a plurality of coiled springs parallel-arranged at regular intervals on the circumferences of the opposite disks, and fixed thereto. The “cage roll” thus made is so placed relative to a net-like web to be expanded from side to side that the opposite disks are inclined toward each other symmetrically with respect to the center line of the net-like web, which is being fed from the upstream side of the expander. While the “cage roll” rotates, the coiled springs are sequentially put in contact with the traveling web in synchronism with the traveling speed of the web, thereby making the web to be forcedly expanded from side to side. Specifically the web is laid on the coiled springs of sequentially increasing length, and hence sequentially increasing spiral pitch (ring-to-ring distance), thereby sequentially stretching the series of wavy-contact portions of the web toward the required width.
The conventional expanders, however, cannot laterally expand web fibers evenly.
In view of this one object of the present invention is to provide a web expander which can laterally expand and distribute web fibers evenly across the required width.